Crystal Structure of a Lanthanum(III) Complex with Pyrazine-2-Carboxylate and Water Ligands

Abstract

The structure of (aqua-O)di(pyrazine-2-carboxylate-N,O-μ-O)mono(pyrazine-2-carboxylate-N,O)lanthanum (III) dihydrate contains La(III) ions, each coordinated by three pyrazine-2-carboxylate (PYR) ligands via their N,O bonding moieties and a water molecule forming an La(PYR)₃·(H₂O) structural unit. In addition, each La(III) ion is coordinated by two carboxylate oxygen atoms each belonging to a ligand chelated to a different adjacent metal ion, giving rise to a bridging system. Three bridging paths are observed: one links the structural units into pairs, the others link the pairs into molecular sheets. The carboxylate group of the third ligand coordinates only one carboxylate oxygen atom leaving the second unbonded to the metal ion. The coordination number of the La(III) ion is nine. Solvation and coordinated water molecules participate in a network of hydrogen bonds which also contributes to the stability of the molecular arrangement.

Keywords:

• Lanthanum(III) complexes
• Pyrazine-2-carboxylate ligand
• X-ray diffraction